Polyaphron fuel compositions

ABSTRACT

A fuel composition which comprises a biliquid foam consisting of from 10% to 97.5% by weight of non-coalescing droplets of a non-polar liquid comprising a petroleum derivative, paraffin or a liquid halogenated hydrocarbon and from 2 to 87% by weight of a continuous phase polar liquid comprising a C 1 -C 3  alcohol, a C 4  alcohol containing at least two hydroxy groups, or ethylene glycol, or mixtures thereof, in an amount of from 60% to 100% by weight thereof, wherein the biliquid foam is stabilized with an amount of from 0.5 to 3.0% by weight based on the total formulation of a surfactant which is selected from castor oil/poly(alkylene glycol) adducts containing from 20 to 50 alkoxy groups, or hydrogenated castor oil/poly(alkylene glycol) adducts containing from 20 to 60 alkoxy groups, or mixtures thereof.

The present invention relates to polyaphron (or biliquid foam)compositions and in particular to polyaphron fuel compositions whichhave a high level of an organic oxygenate in the continuous phase.

Nitrogen oxides comprise a major irritant and pollutant in theatmosphere. Environmental pressures and government regulations haveincreased the need to reduce NO_(x) emissions from internal combustionengines. One problem with using diesel-fuelled engines is thatrelatively high temperatures are reached during combustion, therebyincreasing the tendency of nitrogen from the air, or from nitrogencompounds present in the fuel, to be oxidised to nitrogen oxides.Various methods have been preposed for reducing the production ofNO_(x), including the use of catalytic convertors, the use of cleanfuels, the adjustment of the engine tuning etc. These methods have notachieved a widespread use. The rate at which nitrogen oxides areproduced is related to the combustion temperature and a small reductionin combustion temperature can result in a large reduction in theproduction of nitrogen oxides.

Emulsified fuels have been shown to provide significant advantages inrelation to the control of emissions from internal combustion engines,particularly NO, emissions, by lowering the peak combustion temperatureof the fuel.

The emulsified fuel compositions which have previously been proposed inthe art are water-in-oil emulsions. For example, U.S. Pat. No. 5,669,938discloses a fuel composition which consists of (i) a water-in-oilemulsion comprising a major proportion of a hydrocarbonaceous middledistillate fuel and about 1 to 40 volume percent water (ii) aco-emission and particulate reducing amount of at least one fuel-solubleorganic ignition improver and other optional ingredients.

EP-B-0475620 discloses a diesel fuel composition which comprises (a) adiesel fuel, (b) 1.0 to 3.0 weight percent of water based upon thediesel fuel, (c) a cetane number improver additive in an amount of up toless than 20.0 weight percent based upon the water, and (d) 0.5 to 15weight percent based upon the diesel fuel of a mixed surfactant systemas defined.

EP-A-0561600 discloses a water-in-oil emulsion comprising adiscontinuous aqueous phase containing at least one oxygen-supplyingcomponent such as ammonium nitrate, a continuous organic phasecomprising at least one carbonaceous fuel, and a minor emulsifyingamount of at least one emulsifier as defined.

WO-A-01/04239 discloses a process for making an aqueous hydrocarbon fuelcomposition comprising: (A) mixing a normally liquid hydrocarbon fueland at least one chemical additive to form a hydrocarbon fuel-additivemixture; and (B) mixing the hydrocarbon fuel-additive mixture with waterunder high shear mixing conditions in a high shear mixer to form saidaqueous hydrocarbon fuel composition, said aqueous hydrocarbon fuelcomposition including a discontinuous aqueous phase, said discontinuousaqueous phase being comprised of aqueous droplets having a mean diameterof 1.0 micrometres or less.

WO-A-00/15740 discloses an emulsified water-blended fuel compositioncomprising (A) a hydrocarbon boiling in the gasoline or diesel range,(B) water, (C) a minor emulsifying amount of at least one fuel solublesalt made by reacting an acylating agent having about 16 to 500 carbonatoms with ammonia or an amine, and (D) about 0.001 to 15% by weight ofthe water-blended fuel composition of a water-insoluble amine saltdistinct from component (C).

The water-in-oil emulsified fuels of the prior art suffer from somesignificant disadvantages.

First, they need to contain high levels of emulsifiers to generatestable systems. Investigations have shown that the effectiveness of thereduction in NO_(x)-emissions depends upon the stability of theemulsion. For a reliable operation it is necessary to create an emulsionwith a minimum stability of more than 13 minutes. Secondly, because thecontinuous phase is oil and not water they do not present the ignitionsource with the water first and therefore do not cool the chargeimmediately, resulting in the less efficient use of the water containedin the emulsion to give a cleaner burn. Thirdly, there is a limit to thelevel of organic oxygenate compounds that can be included in thesesystems because of stability issues. These fuels suffer from a sluggishdrive compared to a standard fuel which is a particular disadvantage insituations where power-loss can be unacceptable, such as non-staticengines.

Biliquid foams are known in the art in which small droplets of anon-polar liquid such as an oil are encapsulated in asurfactant-stabilized film of a hydrogen bonded liquid, such as water,and separated from one another by a thin film of the hydrogen bondedliquid. The water or other hydrogen bonded liquid thus forms thecontinuous phase in biliquid foam compositions.

U.S. Pat. No. 4,486,333 discloses a method for the preparation ofbiliquid foam compositions which may comprise the non-polar liquid in atotal amount of about 60% to about 98% by volume, the hydrogen bondedliquid constituting the balance. The non-polar liquid may comprise apetroleum derivative, paraffin or a liquid halogenated hydrocarbon. Thebiliquid fuel composition prepared comprising 96% by volume methanol and4% by volume water had a limited stability of only several days.

Accordingly, there is a need to generate cleaner fuels with loweremissions, especially in the diesel fuel sector. There is also arequirement from the consumer not to compromise on the power output ofthe fuel. There is also a desire for safer fuels and, in particular,fuels with a reduced or more acceptable odour.

We have now developed a biliquid fuel composition which meets theserequirements and which comprises an aqueous continuous phase with a highalcohol level. This results in a more acceptable odour, lower emissionsand a safer fuel with no loss of power. The bifluid fuel composition issafer to the environment as it has a polar continuous phase, andtherefore in the case of spillage it can be washed away as it is waterdisperisble. The presence of organic oxygenates will also lower thefreezing point compared to a fuel in water only composition.Furthermore, the bifluid fuel composition which we have developed hasimproved storage stability as compared with the prior art compositionsdisclosed in U.S. Pat. No. 4,486,333.

Accordingly, the present invention provides a fuel composition whichcomprises a biliquid foam consisting of from 10% to 97.5% by weight ofnon-coalescing droplets of a non-polar liquid comprising a petroleumderivative, paraffin or a liquid halogenated hydrocarbon and from 2 to87% by weight of a continuous phase polar liquid comprising a C₁-C₃alcohol, a C₄ alcohol containing at least two hydroxy groups, orethylene glycol, or mixtures thereof, in an amount of from 60% to 100%by weight thereof, wherein the biliquid foam is stabilized with anamount of from 0.5 to 3.0% by weight based on the total formulation of asurfactant which is selected from castor oil/poly(alkylene glycol)adducts containing from 20 to 50 alkoxy groups, or hydrogenated castoroil/poly(alkylene glycol) adducts containing from 20 to 60 alkoxygroups, or mixtures thereof.

The biliquid fuel of the present invention preferably comprises from 60%to 90% by weight of the fuel, more preferably from 75% to 85% by weightof the fuel. The preferred fuel for use in the present invention isdiesel, gasoline or kerosene.

The polar liquid preferably comprises from 50% to 99% by weight of theC₁-C₄ alcohol or ethylene glycol, or mixtures thereof. The balance ofthe polar liquid is preferably water, in particular deionized water. Thepreferred polar liquids for use in the invention are methanol orethanol, or mixtures thereof.

The particular classes of surfactant used in the present invention havebeen selected for use because of their ability to assist in thepreparation of the biliquid fuel compositions and because they impartlong term stability (e.g. 30 to 90 days) upon the majority of thebiliquid fuel compositions of the present invention prepared using them.

The preferred classes of surfactants for use in the present inventionare hydrogenated castor oil/polyethylene glycol adducts containing from25 to 50 ethoxy groups, more preferably 40 to 45 ethoxy groups or castoroil/polyethylene glycol adducts containing from 25 to 45 ethoxy groups.

It will be understood by those skilled in the art that the choice ofsurfactant will also depend upon the particular fuel and the particularpolar liquid and the amount thereof which are used in the preparation ofthe bifluid fuels.

Polyisobutylene succinimide esters or polyisobutylene succinimide aminesor Mannich bases, known to those skilled in the art as ashlessdispersants, may be used as co-surfactants in the present invention.

The preferred amount of surfactant for use in the present invention isabout 1% by weight based on the total formulation.

The biliquid fuel compositions of the present invention may also containother additives such as preservatives (for instance to preventmicrobiological spoilage), corrosion inhibitors, lubricity improvescleaning/detergent additives, urea and other additives These additivesmay be included in the non-polar liquid or the continuous phase toenhance the performance and address legislative requirements.

It will be understood that the inclusion of these additives will be atthe levels and with the type of materials which are found to beeffective and useful. Care needs to be taken in the choice and amount ofthese additives to prevent compromise to the other performanceadvantages of the present invention.

Methods of producing biliquid foams are described in U.S. Pat. No.4,486,333 involving the preliminary formation of a gas foam in order toprovide a sufficiently large surface area on which the biliquid foam cansubsequently be formed. It has been found that the prior formation of agas foam is not required to manufacture a stable biliquid foam, providedthat a suitable stirring mechanism is provided in the manufacturingvessel. An important aspect of the present invention is the ability tomanufacture biliquid foams suitable for use as a fuel compositionwithout the preliminary formation of gas foam, by the use of a tankincorporating a suitable stirring mechanism.

Such an apparatus comprises a tank provided with a stirrer in which thestirrer blade breaks the interface between the liquid and air. Adelivery device is provided through which the oil phase (non-polarliquid), which will comprise the internal phase of the dispersion isdelivered to the tank. The design of the delivery device is such thatthe rate of addition of the internal phase fluid can be controlled andvaried during the production process. A feature of the productionprocess is that the internal (oil) phase is added to the stirred aqueousphase slowly at first until sufficient droplets have been formed toconstitute a large, additional surface area for the more rapid formationof new droplets. At this point, the rate of addition of the oil phasemay be increased.

The present invention will be further described with reference to thefollowing Examples.

EXAMPLES 1 TO 24 AND COMPARATIVE EXAMPLES A TO C

Biliquid fuel composition were prepared in 50 g batches by adding to a250 ml squat beaker of 67 ml internal diameter a premixed andhomogeneous methanol, ethanol and/or ethylene glycol-water mixture andsurfactant. A 4 blade axial flow impeller of diameter 55 mm was loweredinto the beaker to agitate the aqueous phase ensuring that the impellercut the air/liquid interface and was rotated at 200 rpm. The fuel wasslowly added dropwise to the aqueous phase over a ten to fifteen minuteperiod of time. After all of the fuel had been added, the mixture wasstirred for a further fifteen minutes to form the desired biliquid fuelcompositions.

The results obtained for compositions comprising 80% by weight diesel,1% by weight surfactant and 19% by weight of alcohol-water mixture aregiven in Table 1 below. The percentage column in Table 1 for the alcoholrefers to the percentage in the alcohol-water mixture.

In Comparative Examples A, B and C, the compositions comprise thesurfactants Protachem CAH-16, Etocas 15 and Protachem CA-200, which donot fall within the scope of the present invention.

Where stability is given in days this is the point at which instabilityoccurred. Where it is stated with ‘+’ after the number, this means thatthe sample has not been observed to be unstable in that time and storageis ongoing. All samples were monitored for storage stability at ambienttemperature. (ca.20-25° C.). TABLE 1 Stability Ex. No. Alcohol (%)Surfactant in days Comments on stability. 1 Ethanol 70 Croduret 50 91+Only slight oil on surface. 2 Ethanol 80 Croduret 50 91+ Some foamingand slight oil on surface. 3 Ethanol 85 Croduret 50 85+ Some oil onsurface. After 81 days some decomposition on the upper layer is noticed.4 Ethanol 90 Croduret 50  8   After 8 days sample begins to show somesigns of decomposition. 5 Methanol 70 Croduret 50 90+ Only slight oil onsurface. 6 Methanol 80 Croduret 50 90+ Some oil on surface. 7 Methanol90 Croduret 50 90+ Some oil on surface. 8 Methanol 100 Croduret 50 44  After 44 days the amount of oil begins to increase on surface. Afterthat sample begins slowly to decompose. 9 Ethylene- 70 Croduret 50 82+No changes. glycol 10 Ethylene- 80 Croduret 50 82+ Some foaming, noother changes. glycol 11 Ethylene- 90 Croduret 50 82+ No changes. glycol12 Ethylene- 95 Croduret 50 82+ Some foaming, slight oil on surface.glycol 13 Ethanol 35 Croduret 50 69+ No changes. Methanol 35 14 Ethanol35 Croduret 50 69+ No changes. Ethylene 35 glycol 15 Ethanol 70 Croduret25 70+ Some oil on surface. 16 Ethanol 70 Croduret 25* 70+ Slight oil onsurface. 17 Ethanol 70 Croduret 25** 70+ Some oil on surface. 18 Ethanol70 Croduret 40LD 15+ No changes. 19 Ethanol 70 Protachem 15+ No changes.CAH-60 20 Ethanol 70 Etocas 25  3   After three days, the amount of freeoil begins to increase. 21 Ethanol 70 Protachem  3   After 6 days a lotof free oil on CA-30 surface, and some decomposition. 22 Ethanol 70Etocas 35 48   After 48 days decomposition of sample leading to free oiland instability. 23 Ethanol 70 Etocas 40 18   After 18 days gradualdecomposition begins. 24 Ethanol 70 Protachem 60+ Beginning to decomposegradually, but CA-40 still stable overall. Comp A Ethanol 70 Protachem<1  Begins to decompose gradually. CAH-16 Comp B Ethanol 70 Etocas 15few min Product is stable for 5-10 minutes. Comp C Ethanol 70 Protachemfew min Stable only for a few minutes. CA-200

EXAMPLE 25

The procedure of Example 1 was repeated substituting unleaded petrol forthe diesel fuel. The resulting biliquid fuel was stable for 64 daysafter which some instability was seen.

EXAMPLE 26

The procedure of Example 1 was repeated substituting kerosene for thediesel fuel. The resulting biliquid fuel was stable for 43 days afterwhich the sample began to show some signs of instability.

EXAMPLE 27

The procedure of Example 1 was repeated for a composition comprising 75%by weight of diesel fuel, 1% by weight of Croduret 50 and 24% by weightof an ethanol-water mixture comprising 70% by weight of ethanol. Theresulting bifluid fuel was stable for over 123 days.

EXAMPLES 28 TO 32

The procedure of Example 1 was repeated for compositions comprising 85%by weight of diesel fuel, 1% of a surfactant and 14% by weight of analcohol-water mixture. The results are given in Table 2 below. Thepercentage column in Table 1 for the alcohol refers to the percentage inthe alcohol-water mixture. TABLE 2 Ex. Stability No. Alcohol (%)Surfactant in days Comments on stability. 28 Ethanol 70 Croduret 126+Stable. 50 29 Isopropyl- 70 Croduret 125+ Stable, with slight alcohol 50oil on surface 30 Ethanol 70 Croduret 169+ Stable, with slight 25 oil onsurface 31 Ethanol 70 Protachem 126+ Stable CAH-60 32 Ethanol 70Croduret 126+ Stable 40 LDFootnotes to Tables 1 and 2* The surfactant was added to the oil phase** The surfactant was included in both phases (50:50)

Croduret 25, Croduret 40LD and Croduret 50 are Trade Names forhydrogenated castor oil/polyethylene glycol adducts available from CrodaChemicals Limited where the suffixes 25, 40LD and 50 refer to increasingnumbers of ethylene oxide groups in the polyethylene oxide chain.

Etocas 15, Etocas 25, Etocas 35 and Etocas 40 are Trade Names for castoroil/polyethylene glycol adducts available from Croda Limited where thesuffixes 15, 25, 35 and 40 refer to the number of ethylene oxide groupsin the polyethylene oxide chain.

Protachem CA-30, Protachem CA-40 and Protachem CA-200 are Trade Namesfor castor oil/polyethylene glycol adducts available from ProtameenChemicals Inc. where the suffixes CA-30, CA-40 and CA-200 refer to thenumber of ethylene oxide groups in the polyethylene oxide chain.

Protachem CAH-16 and CAH-60 are a Trade Names for a hydrogenated castoroil/polyethylene glycol adducts available from Protameen Chemicals Inc.where the suffix CAH-16 and CAH-60 refers to the number of ethyleneoxide groups in the polyethylene oxide chain.

COMPARATIVE EXAMPLE D

The teaching of Example 7 of U.S. Pat. No. 4,486,333 was repeated. Abiliquid fuel composition was prepared by making a 0.5% solution of asilicone block copolymer L5614 in 96% methanol, foaming 5 ml of thissolution and gradually adding thereto 45 ml of kerosene containing 0.1%Tergitol 15-S-3 with vigorous shaking after each addition of the oilphase.

The sample inverted after the addition of 75% (about 34 ml) of the oilphase.

EXAMPLE 33

The teaching of Example 7 of U.S. Pat. No. 4,486,333 was modified usingas the sole surfactant 1% Croduret 50 in 96% methanol.

A bifluid fuel composition was prepared by stirring 5 ml of the methanolsolution and gradually adding thereto 45 ml of kerosene using thestirring method as described in Example 1. After all of the fuel hadbeen added, the mixture was stirred at 300 rpm for a further 15 minutesto form the bifluid fuel composition.

The formulation remained stable for three weeks.

EXAMPLES 34 TO 37

Examples 35 to 38 illustrate the preparation of bifluid fuelcompositions using isopropyl alcohol/water andisopropylalcohol/ethanol/water mixtures as the polar liquid.

The bifluid fuels were prepared according to the teaching of Example 1but with an addition time for the oil phase of 20 minutes and anadditional stirring time of 20 minutes after completion of the oiladdition. Examples 36 and 37 were prepared as 25 g batches. The resultsobtained for compositions comprising 80% by weight of diesel, 1% ofsurfactant and 19% of an alcohol/water mixture are given in Table 3below. The percentage column in Table 3 for the alcohol refers to thepercentage in the alcohol-water mixture. TABLE 3 Ex. Stability No.Alcohol (%) Surfactant in days Comments on stability. 34 Isopropyl 70Croduret 16 Slight decomposition in upper layer after 5 days alcohol 50leading to progressive deterioration. 35 Isopropyl 65 Croduret 59 Slightdecomposition in upper layer at first alcohol 50 after 28 days leadingto progressive decomposition. 36 Isopropyl 35 Croduret 11 Free oil onthe surface of sample at first alcohol 50 followed by decomposition.Ethanol 35 37 Isopropyl 42 Croduret 11 Separation into two layers givingrapid alcohol 50 decomposition. Ethanol 28

EXAMPLE 38 TO 42

Examples 38 to 42 illustrate the preparation of bifluid fuelcompositions using butylene glycol/water, butylene glycol/ethyleneglycol/water or propylene glycol/water mixtures as the polar liquid.

The bifluid fuels were prepared according to the teaching of Example 1but with an addition time for the oil phase of 20 minutes and anadditional stirring time of 20 minutes after completion of the oiladdition. The results obtained for compositions comprising 80% by weightof diesel, 1% of surfactant and 19% of the glycol/water mixture aregiven in Table 4 below. The percentage column in Table 4 for the glycolrefers to the percentage in the glycol-water mixture. TABLE 4 Ex.Stability No. Alcohol (%) Surfactant in days Comments on stability. 38Butylene 35 Croduret 40+ Stable. glycol 50 Ethylene 35 glycol 39Butylene 50 Croduret 40+ Stable. glycol 50 Ethylene 20 glycol 40Butylene 60 Croduret 40+ Stable. glycol 50 41 Butylene 70 Croduret 39+Stable. glycol 50 42 Propylene 70 Croduret 39+ Stable. glycol 50

EXAMPLE 43

A bifluid fuel composition was prepared using the stirring method asdescribed in Example 1 as a 25 g sample using 80% by weight of keroseneJet A1 fuel, 1% by weight Croduret 50 and 19% by weight of a 96%methanol-4% water (by weight) mixture. The addition of the oil phase wascarried out over a 20 minute period and the composition was stirred foran additional 20 minutes after completion of the oil addition.

The resulting composition was stable for 32 days after which time therewas decomposition leading to progressive deterioration.

1. A fuel composition which comprises a biliquid foam consisting of from10% to 97.5% by weight of non-coalescing droplets of a non-polar liquidcomprising a petroleum derivative, paraffin or a liquid halogenatedhydrocarbon and from 2 to 87% by weight of a continuous phase polarliquid comprising a C₁-C₃ alcohol, a C₄ alcohol containing at least twohydroxy groups, or ethylene glycol, or mixtures thereof, in an amount offrom 60% to 100% by weight thereof, wherein the biliquid foam isstabilized with an amount of from 0.5 to 3.0% by weight based on thetotal formulation of a surfactant which is selected from castor oil/poly(alkylene glycol) adducts containing from 20 to 50 alkoxy groups, orhydrogenated castor oil/poly(alkylene glycol) adducts containing from 20to 60 alkoxy groups, or mixtures thereof.
 2. A fuel composition asclaimed in claim 1 wherein the amount of surfactant is about 1% byweight based on the total formulation.
 3. A fuel composition as claimedin claim 1 wherein the surfactant comprises a hydrogenated castoroil/polyethylene glycol adduct containing from 25 to 50 ethoxy groups.4. A fuel composition as claimed in claimed in claim 3 wherein thehydrogenated castor oil/polyethylene glycol adduct contains from 40 to45 ethoxy groups.
 5. A fuel composition as claimed in claim 1 whereinthe surfactant comprises a castor oil/poly(alkylene glycol) adductcontaining 25 to 45 ethoxy groups.
 6. A fuel composition as claimed inclaim 1 wherein the polar liquid comprises from 70% to 99% by weight ofthe C₁-C₄ alcohol or ethylene glycol.
 7. A fuel composition as claimedin claim 6 wherein the balance of the polar liquid comprises water.
 8. Afuel composition as claimed in claim 1 wherein non-polar liquidcomprises from 60% to 90% by weight of the biliquid foam.
 9. A fuelcomposition as claimed in claim 8 wherein the non-polar liquid comprisesfrom 75% to 85% by weight of the biliquid foam.
 10. A fuel compositionas claimed in claim 1 wherein the non-polar liquid comprises diesel,gasoline or kerosene fuel.
 11. A fuel composition as claimed in claim 1wherein the C₁-C₄ alcohol is methanol or ethanol or a mixture thereof.